Multiple speed motor and multiple coil starting control



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MULTIPLE SPEED MOTOR AND MULTIPLE COIL STARTING CONTROL June 18, 1968 2Sheets-Sheet 2 Filed Oct. 21. 1965 nnuuf INVENTOR.

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United States Patent 3,389,316 MULTIPLE SPEED MOTOR AND MULTIPLE COILSTARTING CONTROL Alfred B. Roby, Dayton, Ohio, assignor to GeneralMotors Corporation, Detroit, Mich., a corporation of Delaware Filed Oct.21, 1965, Ser. No. 499,475 7 Claims. (Cl. 318-221) ABSTRACT OF THEDISCLOSURE In the preferred form, a three-coil electromagnetic startingrelay is provided for controlling the energization of the starting orphase winding of a selective twospeed induction motor. One of thesecoils is at all times connected in series with the low speed winding,while the other two coils are respectively connected in series with thehigher speed and lower speed contacts of the double throw selectorswitch. The starting relay operates a make before break double throwswitch having its movable contact connected in series with the coilwhich is in series with the low speed selector switch contacts and whichhas one of its relatively stationary contacts connected to the coil inseries with the lower speed main winding. The other relativelystationary contact of the relay is connected to the higher speed mainwinding circuit between the coil connected to the higher speed contactof the selector switch and the higher speed main winding. The startingrelay also closes a normally open single throw starting switch connectedin series with the starting or phase winding.

This invention pertains to a selective control system for multiplespeedinduction motors and more particularly to an electro-magneticcontrol system for cutting in and out the starting winding at the mostdesirable switching speeds for any selected maximum speed of themultiple speed induction motor.

For some applications it is not completely satisfactory to use acentrifugal type of selective multi-speed motor control system such asis illustrated in Patent 3,153,184 issued Oct. 3, 1964. For example, thenecessity of physically associating the centrifugal switch with themotor may make the centrifugal switch relatively inaccessible forservice and replacement. Also, the simple centrifugal switch indicatedin said patent is capable of operating substantially only at a singlespeed, normally about 0.8 of the maximum speed provided by the lowspeedwinding. This switching speed provides satisfactory operation foroperation upon the low speed winding but this centrifugal switch willnot be satisfactory for the high speed winding circuit whenever heavyloads are encountered. The reason for this is to obtain satisfactoryacceleration, under load it is desirable to maintain the startingwinding energization at all speeds below about 0.8 of the maximum speedprovided by the high speed winding. Since the centrifugal switchneeds'to be set to open the starting circuit at about 0.8 of the maximumspeed provided by the low speed winding, for example 900 r.p.m., thestarting or phase winding can not be energized by such a centrifugalswitch above that speed even though it is desirable that the starting orphase winding in high speed operation be energized at all speeds belowabout 1500 rpm. with 4 and 6 pole induction motors for example. Thefailure to reenergize the starting or phase winding upon a fall in speeddue to heavy load may cause over-heating of either running winding anddamage the motor.

It is an object of this invention to provide a simple satisfactoryelectro-r'nagnetic starting control for a selective double woundmultiple speed induction motor which will provide for the energizationand reenergization of the 3,389,316 Patented June 18, 1968 below 0.8maximum speed for the lower speed operation I and which for higher speedoperation will maintain and reenergize the starting or phase windingenergization whenever the speed is below 0.8 maximum speed for thehigher speed operation which is between the maximum speed for the lowerspeed and higher speed operation to assure maximum performance of themotor without damage in either selected normal operating speed.

These and other objects are attained in the form shown in the drawingsin which a 3-coil electromagnetic starting relay is provided forcontrolling the energization of the starting or phase winding of aselective 2-speed induction motor. One of these coils is at all timesconnected in series with the low speed winding, while the other twocoils are respectively connected in series with the higher speed andlower speed contacts of the double throw selector switch. The startingrelay operates a make before break double throw switch having itsmovable contact connected in series with the coil which is in serieswith the lower speed selector switch contacts and which has one of itsrelatively stationary contacts connected to the coil in series with thelower speed main winding. The other relatively stationary contact of therelay is con nected to the higher speed main winding circuit between thecoil connected to the higher speed contact of the selector switch andthe higher speed main winding. The starting relay also closes a normallyopen single throw starting switch connected in series with the startingor phase winding.

With this arrangement, when the higher speed main winding circuit isselected by the selector switch, the coil in this higher speed circuitacts alone to keep the starting switch closed at all speeds below about0.8 of the high speed which is normally about 0.8 of the maximum highspeed. When the lower speed main winding is selected, a second coildetermines the speed at which the starting switch opens the starting orphase winding circuit under low speed operation while both this coil andthe coil in series with the lower speed main winding determine the speedat which the starting contacts will reclose the main winding circuitupon an increase in load and also will pull in the relay after a periodof idleness. When the two coil system is used the two coils in serieswith the higher and lower speed contacts of the selector switch areshorted out or eliminated and the control is provided by the coil inseries with the low speed main winding and a coil in series with bothwindings provide for closing of the starting switch at all speeds belowthe balance speed for low speed operation.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein preferred embodiments of the present invention areclearly shown.

In the drawings:

FIGURE 1 is a Wiring diagram illustrating my improved selective controlsystem for a 2-speed induction motor arranged for the use of the threecoils with the energized circuits for high speed operation illustratedin heavy lines.

FIGURE 2 is a wiring diagram similar to FIGURE 1 but showing thecircuits arranged for low speed operation and similarly illustrated withthe energized circuits shown in heavy lines.

FIGURE 3 is a wiring diagram similar to FIGURES 1 and 2 with two of thecoils shunted out and a fourth coil rendered effective and with theselector switch in the higher speed position and with the energizedcircuits shown in heavy lines; and,

FIGURE 4 is a wiring diagram similar to FIGURES 13 with the energizationof the coils similar to FIGURE 3 with the selector switch in the lowerspeed position and the energized circuits shown in heavy lines.

Referring now to the drawings and more particularly to FIGURE 1, thereis illustrated a wiring diagram having supply conductors L-l and L-2.Connected to the supply conductor L-l is a double throw single poleselector switch having a manually operably movable contact 22 connectedto the supply conductor L-1 which is adapted selectively to make contactwith the higher speed normally stationary contact 24 or with the lowerspeed normally stationary contact 26. The contact 24 is connectedthrough the conductor 28 and a relay coil 30 and a conductor 32 with oneterminal of the higher speed main winding 34. The lower speed selectorcontact 26 is connected through a conductor 36 and a coil 38 with themovable contact 40 of a make before break double throw electromagneticoperated switch having alternately engaged leaf spring contacts 42 and44. The leaf spring contact 44 is connected through the conductor 46,the relay coil 48 and the conductor 50 with one terminal of the lowerspeed main winding 52, of the multiple speed induction motor 54. Thesecond terminals of the lower and higher speed main windings 34 and 52are joined together at the junction 56 and connected by the conductor58, the switch 60 and the conductor 62 with the supply conductor L-2.The lower leaf spring contact 42 in FIGURE 1 is connected by theconductor 64 to the conductor 32 which connects the coil 30 with theadjacent terminal of the higher speed main winding 34. A startingcircuit has a conductor 66 connecting the supply conductor L-l to thestarting switch 68 which in turn connects through the conductor 70, thecapacitor 72 and the conductor 74 with one terminal of the starting orphase winding 76. The opposite terminal of this winding 76 is connectedby the conductor 78 to the supply conductor L-2.

The electromagnetic coils 30, 38 and 48 are associatedelectromagnetically in relation to a common core 80 of magnetic materialwhich is capable of attracting the armatures 82 and 84 for operating thestarting switch 68 and the movable contact 40 of the double throw relayswitch which includes the leaf spring contacts 42 and 44. The coil 30 isarranged to have the proper number of effective turns to effect theattraction of the armatures 82 and 84 at the current flow for all speedsbelow 0.8 the maximum speed for high speed operation upon the higherspeed main winding 34. This current flow will vary for various types andsizes of 2-speed motors, examples of which are illustrated in theaforementioned Patent 3,153,- 184 as well as in Patents 2,999,954 and2,999,955, both issued Sept. 12, 1961. For example, if the motor 54 hasa 4-pole high speed arrangement providing a maximum speed of about 1750r.p.m., the coil 30 will cause the starting switch 68 and the contacts40 and 42 to be closed for the starting period at all speeds below about0.8 of the maximum speed or below 1400 rpm. This will assure maximumacceleration and torque from the start to full speed and will alsoassure that the starting or phase Winding 76 will be reenergized duringthe running period should the motor speed at any time fall below 1400rpm. by the reclosing of the starting switch 68 to energize the startingof phase winding 76.

For lower speed operation, the movable contact 22 of the selector switch20 is moved into engagement with the lower speed contact 26 to energizethe conductor 36 and the coil 38, FIGURE 2. Current will continuethrough the conductor 39 to the movable contact 40 of the double throwrelay switch. When the motor 54 is idle, the contact 40 will be inengagement with the upper leaf spring contact 44 to conduct current uponenergization through the conductor 46, the coil 48, the conductor 50,the lower speed main winding 52, the conductor 58, the switch 60 and theconductor 62 to the supply conductor L-2. The energization of the coils48 and 38 will immediately attract the armatures 82 and 84 therebyenergizing for the starting period the starting or phase winding circuitthrough the conductors 66, the switch 68, the conductor 70, thecapacitor 72, the conductor 74, the starting or phase winding 76 and theconductor 78.

The attraction of the armature 82 will move the movable contact 40 intoengagement with the lower leaf spring contact 42 and slightly thereafterdisengage itself from the upper leaf spring contact 44. By thisswitching the current no longer flows through the coil 48 and the lowerspeed winding 52, but is diverted for the starting period through theconductors 64 and 32, the higher speed main winding 34 and conductors58, the switch 60 and the conductor 62 to the supply conductor L-2. Thestarting or phase winding 76 and the higher speed main winding 34 remainenergized through these circuits until 0.8 maximum speed is reached foroperation upon the lower speed winding 52. The coil 38 has the propernumber of turns to hold the armatures 82 and 84 attracted as long as themotor 54 operates upon the higher speed main winding 34 below this 0.8maximum speed, for example 900 rpm, for low speed operation. When this0.8 maximum speed for low speed operation is reached, the coil 38 willnot be strong enough to hold the armatures 82 and 84 thereby allowingthe starting switch 68 to open and allowing the movable contact 40 toreengage the upper leaf spring contact 44 and to disengage itself fromthe lower leaf spring contact 42. This will reenergize the lower speedmain winding 52 for the running period through the conductor 46, and thecoil 48, the conductor 50, the lower speed main winding 52 of the motor54. Should the motor speed slow down, the reclosing of the startingconductors 68 and also the contacts 40 and 42 will be determined by theturns of the coils 38 and 48. As mentioned previously, the coil 38 hasthe proper number of turns to release the main winding at a currentcorresponding to 0.8 of the maximum speed for lower speed operation suchas 1150 rpm. The coil 48 has a proper number of turns which when addedto the magnetic effect of the coil 38 upon the smaller current flowingthrough the lower speed winding 52 below 0.8 maximum low speed willcause the attraction of the armatures 82 and 84 to restore the startingcircuit. This will prevent excessive flow of current through the lowerspeed winding 52 under heavy load and also increases the availabletorque at the lower speeds.

The electromagnetic relay system may be reducd to two operating coils(FIGURE 3) by closing the switches 88 and 90 which shunt the coils 38and 30 and by opening the switch 60 to effectively connect the coil 92in series with the conductors 58 and 62 as well as both the higher andlower speed main windings 34 and 52. This provides an electromagnetictype of control system for a selective 2-speed induction motor whichprovides a phase winding control similar to that provided by thecentrifugal switch in Patent 3,153,184. The reduction in the number ofcoils reduces the maximum performance in the higher speed operation butprovides equally good performance in the lower speed operation. It alsoretains the full advantages of the electromagnetic type of control. Whenthe double throw contact 22 of the selector switch 20 moves intoengagement with the higher speed stationary contact 24, current willflow through the conductor 28, with switch 90, the conductor 32, thehigher speed main winding 34, the conductor 58, the coil 92 and theconductor 62 to the supply conductor L-Z. This energization of the coil92 will cause the armatures 82 and 84 to be attracted to close thestarting or phase winding circuit to energize the starting or phasewinding 76 during the starting period. Upon reaching 0.8 maximum lowspeed of about 900 r.p.m., the coil 92 will release the armatures 82 and84 to deenergize the phase winding 76. The motor continues itsacceleration above 900 r.p.m. during the running period with the higherspeed main winding 34 alone until maximum speed of about 1750 r.p.m. isreached. Upon any fall in speed below about 0.8 maximum low speed of 900r.p.m. the armature 84 is again attracted to reenergize starting orphase winding 76.

Referring to FIGURE 4, to select the lower speed operation, the movablecontact 22 is moved into engagement with the stationary contact 26 toconduct current from the supply conductor L-l through the conductor 36,the switch 88, the conductor 39, the movable contact 40, the leaf springcontact 44, the conductor 46, the coil 48, the conductor 50, the lowerspeed winding 5-2, the conductor 58, the coil 92 and the conductor 62 tothe supply'conductor L-2. Immediately the armatures 82 and 84 will beattracted to close the starting or phase winding circuit as previouslydescribed and to engage the contacts 40 and 42 to cause current to beconducted through the conductors 64 and 32, the higher speed mainwinding 34, the conductor 58, the coil 92 and the conductor 62 to thesupply conductor L-2. The starting condition then will be similar tothat previously described with reference to FIGURE 3. The starting orphase winding 76 will remain energized until there is reached 0.8maximum low speed of 900 r.p.m. for low speed operation,

At this point, the armatures 82 and 84 will be released thereby causingthe movable contact 40 to reengage the leaf'spring contact 44 toreenergize the lower speed main winding 52 after which it will disengageitself from the leaf spring 42 to deenergize the higher speed mainwinding 34. At the same time the release of the armature 84 will causethe starting switching 68 to reopen to deenergize the starting or phasewinding 76. Should the speed of the motor 52 be reduced below 0.8maximum low speed of 900 r.p.m. due to loading cor-responding to lowspeed operation, the iarmatures 82 and 84 will again be attracted torestore the circuits to the starting condition and thereby preventexcessive current in the low speed main winding. This will increase thetorque and prevent overheating of the windings. While the speeds givenas examples correspond to those of tour and six pole motors, othermultispeed motors can be used such as two and four pole motors. Thus, Ihave provided an electromagnetic controlsuitable for multiple speedinduction motors which will provide for the energization andreenergization of the phase winding in .all the speeds of operationbelow 0.8 maximum low speed for low speed operation when two coils areused and below 0.8 maximum speed for both high and low speed operationwhen three coils are used.

While the embodiments of the present invention as herein disclosed,constitute preferred forms, it is to be understood that other formsmight be (adopted.

What is claimed is as follows:

1 A two-speed electric motor and control system including lower andhigher speed main windings and a phase winding, supply conductors forenergizing said windings, wherein the improvement comprises a doublethrow selector switch having a movable contact connected to one of saidsupply conductors and alternately engageable lower and higher speedcontacts respectively connected to said lower and higher speed mainwindings, a starting relay having normally open con't'acts in serieswith said phase winding and having a first operating coil connected allthe time in series with the lower speed main winding and having a secondoperating coil in series with both said lower and higher speed mainwindings.

2. A two-speed electric motor and control system including lower andhigher speed main windings and a phase Winding, supply conductors forenergizing said windings, wherein the improvement comprises a doublethrow selector switch having a movable contact connected to one of saidsupply conductors and alternately engageable lower and higher speedcontacts respectively connected to said lower and higher speed mainwindings, a starting relay having normally open contacts in series withsaid phase winding and having a first operating coil connected all thetime in series with the lower speed rnain winding and having a secondoperating coil in series with both said lower and higher speed mainwindings, said starting relay also having means effective in response tothe closing of said normally open contacts for dener gizing said firstoperating coil.

3. A-two-speed electric motor and control system including lower andhigher speed main windings and a phase winding, supply conductors forenergizing said windings, .wherein the improvement comprises a doublethrowwselector switch having a movable contact connected to one of saidsupply conductors and alternately engage- -able lower and higher speedcontacts respectively connected to said lower and higher speed mainwindings, a starting relay having normally open contacts in series withsaid phase winding and having a first operating coil connected all thetime in series with the lower speed main winding, said starting relaybeing provided with an additional double throw switch having a movablecontact and first and second alternately engageable relay contacts, saidfirst contact being electrically connected in series with said firstcoil and said lower speed main winding, said second alternatelyengageable relay con- .tact ibeing electrically connected to said higherspeed main winding, said starting relay having a second operating coilconnected in series between said movable relay contact and said lowerspeed contact of said selector switch.

4. A two speed motor and control system including lower and higher speedmain Win-dings and a phase Winding, supply conductors for energizingsaid winding-s, wherein the improvement comprises a double throwselector switch having a movable contact connected to one of the supplyconductors and alternately engageable lower and higher speed contactsrespectively connected to said lower and higher speed main windings, astarting relay having normally open contacts in series with said phasewinding and having first andsecond operating coils in series with saidlower speed main Winding and having a third operating coil connected inseries with said higher speed contact and said higher speed mainwinding.

5. A two speed motor and control system including lower and higher speedmain windings and a phase winding, supply conductors for energizing saidwindings, wherein the improvement comprises a double throw selectorswitch having a movable contact connected to one of the supplyconductors and alternately engageable lower and higher speed contactsrespectively connected to said lower and higher speed main windings, astarting relay having normally open contacts in series with said phasewinding and having first and second operating coils in series with saidlower speed main winding and having a third operating coil connected inseries with said higher speed contact and said higher speed mainwinding, said starting relay also having means effective in response tothe closing of said normallyopen contacts for deenergizing said secondoperating coil.

6. A two speed motor and control system including lower and higher speedmain windings and a phase winding, selector switch means having lowerand higher selective positions for selecting lower or higher speedoperation of said motor, wherein the improvement comprises a startingrelay having a starting position and a running position and having meansfor energizing the phase winding and the higher speed main winding anddeenergizing the lower speed main winding in the starting position, saidstarting relay also having means effective in response to a change fromits starting position to its running position when said selector switchis in its lower selective position for deenergizing said higher speedmain winding and energizing said lower speed main winding, said startingrelay having first and second operating coils connected in series withsaid lower speed main winding and a third operating coil in series withsaid higher speed main winding.

7. A two speed motor and control system including lower and higher speedmain windings and a phase Winding, supply conductors for energizing saidwindings, wherein the improvement comprises, a double throw selectorswitch having a movable contact connected to one of the supplyconductors and alternately engageable lower and higher speed contactsrespectively connected to said lower and higher speed main windings, astarting relay having a first operating coil in series with the lowerspeed main winding and a second operating coil in series with saidhigher speed main winding, said starting relay having a startingposition and a running position, said starting relay having meanseffective in its starting position for energizing said phase Winding andsaid higher speed main winding and deenergizing said first coil whensaid selector switch has its moveable contact in contact with either ofsaid higher or lower speed contacts, said starting relay having meanseffective in its running position for changing the energization of saidphase winding and for deenergizing said higher speed main winding andenergizing said lower speed main winding when said selector switch hasits moveable contact in contact with said lower speed contact, saidstarting relay also having means effective in its running position forchanging the energization of said phase winding and continung theenergization of said higher speed main winding and continuing thedeenergization of said lower speed main winding when said selectorswitch has its moveable contact in contact with said higher speedcontact.

References Cited UNITED STATES PATENTS 2,743,406 4/ 1 95 6 London318-221 XR 2,774,924 12/1956 Witt 318--221 XR 3,049,654 8/1962 Brucken318-224 XR 3,327,192 6/1967 Miller 318-221 ORIS L. RADER, PrimaryExaminer.

G. Z. RUBINSON, Assistant Examiner.

